Cheiron was the only friendly Centaur in greek mythology, and the son of the Titan Cronos who disguised himself as a horse in order to seduce Philyra without his wife Rhea discovering the affair. Unlike other centaurs, who are descended from Ixion, Cheiron was among the gentlest, wisest, and most learned of creatures. As a result, he was asked to tutor several of the greatest of Greek heroes, including Achilles, Asclepius, Heracles, Jason, Aeneas, and Peleus. Being the son of a god he was immortal, but Heracles accidentally wounded him with a poisoned arrow when fighting the other Centaurs. In order to be relieved of the unrelenting torment of the wound, he gave his immortality to the Titan Prometheus and allowed himself to die. He then appealed to Zeus and was transformed into the constellation Sagittarius.